Change text color based on a brightness of the covered background area in HTML?


It is possible to change the textcolour depending on the average brightness of the covered pixels ofits parent's background color by using the following code snippet.

var rgb = [255, 0, 0];
setInterval(display, 1000);
function display() {
   rgb[0] = Math.round(Math.random() * 255);
   rgb[1] = Math.round(Math.random() * 255);
   rgb[2] = Math.round(Math.random() * 255);
   
   var d = Math.round(((parseInt(rgb[0]) * 299) + (parseInt(rgb[1]) * 587) +
      (parseInt(rgb[2]) * 114)) / 1000);
   // for foregound
   var f = (d> 125) ? 'black' : 'white';
   
  // for background
  var b = 'rgb(' + rgb[0] + ',' + rgb[1] + ',' + rgb[2] + ')';
  $('#box').css('color', f);
  $('#box').css('background-color', b);
}
<scriptsrc = "https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<div id = "box"> Demo</div>

The following is the CSS −

#box {
   width: 300px;
  height: 300px;
}

Updated on: 04-Mar-2020

140 Views

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